An analysis of new generation coal gasification projects

International Journal of Mining Science and Technology 22 (2012) 509–515

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An analysis of new generation coal gasification projects Kreynin Efim Vulfovich ⇑ Joint Stock Company Gazprom Promgaz, Moscow 117420, Russia

a r t i c l e

i n f o

Article history: Received 12 November 2011 Received in revised form 15 November 2011 Accepted 17 January 2012 Available online 12 July 2012 Keywords: Underground coal gasification (UCG) UCG technology of the new generation Stability and controllability Clean coal technology

a b s t r a c t The global trends of increasing oil and gas costs have compelled coal possessing countries to start long term underground coal gasification (UCG) projects. These enhance national energy security and are among the cleanest, ecologically safest coal utilization technologies. This paper delineates the major characteristics of such technologies and analyzes technical solutions. Highlighting the desire to develop large scale industrial UCG plants, pilot level projects are presented using a new UCG method developed in Russia by Joint Stock Company Gazprom Promgaz. This method is distinct for its high controllability, stability, and energy efficiency. New, efficient technical solutions have been developed over the last 10–15 years and are patented in Russia. They guarantee controllability and stability of UCG gas production. Over one hundred injection and gas production wells have been operated simultaneously. Ó 2012 Published by Elsevier B.V. on behalf of China University of Mining & Technology.

1. Introduction Underground coal gasification (UCG) can potentially guarantee the energy independence of a country or region having sufficient coal resources. Commercial scale UCG may become a way to dispense with the importing of gaseous and liquid hydrocarbons that continually rise in price. Although 75 years have elapsed since the first UCG field experiments industrial UCG is being practiced nowhere in the world. A major reason for this is the complexity of the UCG physical and chemical process, which takes place deep underground and is influenced by numerous factors and conditions including mining, technical, hydrodynamic, hydro-geological, and chemical ones. A controllable and stable technology is possible only once these numerous influences are taken into account. We formulate, substantiate, and principle technical solutions for a new generation UCG technology based upon an analysis of international UCG practices. This is intended to provide for stable industrial production. 2. Experimental 2.1. Characterization of gasified coal seams A description of coal seams developed using UCG methods in the former USSR, and Russia, is presented in Table 1 [1,2]. A description of some coal seams developed using two-stage UCG methods in China is presented in Table 2 [3]. ⇑ Tel.: +7 495 5044259. E-mail address: [email protected]

A 10 m thick coal seam at a depth of 140 m was gasified in Australia. The gasified coals had the following parameters: a moisture content of 6.8%; an ash content of 19.3%; a volatile content of 40%; and, a combustion value of 23 MJ/kg.

2.2. Characterization of UCG methods In the USSR and Russia coals were gasified using the ‘‘flow’’ method that envisages gasification within a channel. The four sides were the bottom and top of the formation, loose rock, and the combustible coal face [1]. As injection penetrates the channel hydrocarbon and coal volatiles burn to produce carbon dioxide and water. These then react with hydrocarbons of the coke residue and are converted into combustible carbon monoxide, hydrogen, and methane that pass through the channel to the surface. The principal scheme for a gas generator module used in traditional UCG technology is shown in Fig. 1. The principal scheme for a gas generator module used in the new generation of UCG technology is shown in Fig. 2. This scheme was developed by JSC ‘‘Gazprom promgaz’’ over the period from 1996 to 2011. The gas generator is in the plane of the coal seam, which is either inclined or horizontal. The injection well is cased lengthwise and the gas producing well is cased up to the point of coal seam penetration. The lower parts of both these wells are interconnected in single hydraulic system. The combustion face is located at the injection well and the injection supply point moves up the well as the coal seam yields gas. Thus the oxidizer is supplied in a controlled manner directly to the reacting coal face. An active heterogeneous reaction within the channel involving the coal walls

2095-2686/$ - see front matter Ó 2012 Published by Elsevier B.V. on behalf of China University of Mining & Technology. http://dx.doi.org/10.1016/j.ijmst.2012.01.012

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Table 1 General characteristics of coal seams developed by UCG (traditional technology). Gasification site and coal seam

Coal seam depth (m)

Development depth (m)

QH p (MJ/kg)

Coal technical content (%) P

C

W

A

150 200–250 60 75 150 200

14.5 12.1 15.0 15.0 15.5 4.5

7.9 8.0 10.4 17.0 7.6 9.8

39.0 40.0 40.0 39.5 39.0 40.0

22.6 22.8 21.4 20.1 22.3 23.0

8–9 2.2 2.06 3.8

50–300 130–140 210 200–230

6.0 8.0 6.0 4.3

5.2 2.3 2.3 4.3

32.3 32.0 32.0 27.0

29.1 28.9 30.6 30.7

Lignites Podmoskovnay station of Podzemgaz (1947–1962)

2.5

30–80

30.0

34.3

44.5

11.8

Angrenskay station of Podzemgaz (1962–1989, operation continued)

3–20

120–200

35.0

12.2

33.0

15.1

Shatskaya station of Podzemgaz (1965–1974)

2.6

30–60

30.0

26.0

38.1

11.0

Bituminous coals Lisichanskaya station of Podzemgaz (1948–1963) R8 K4 K7 K8 K6 K5

1.8–2.0 1.21 0.44 0.88 0.60 0.80

Yuzhno-Abinskaya station of Podzemgaz (1955–1996) IV internal VIII internal VII internal Burned

Table 2 General characteristics of coal seams developed by UCG (two-stage gasification). Mine

Commencement

Xinhe

1994

Liuzhuang

1996

Xinwen

2000

Xiyang

2001

Coal type

Rich bituminous Gas bituminous Gas bituminous Anthracite

Depth (m)

Thickness (m)

Angle of incidence (°)

80

3.5

68–75

100

2.5–3.5

45–55

100

1.8

25

190

6

22–27

V

U

1 2

3

4 6

5

4

5 Fig. 2. A schematic of a new UCG gas generator. (1) Air injection well cased in the coal seam; (2) Production well without casing in the coal seam; (3) Coal seam; (4) Reaction channel; (5) Slag and collapsed roof formations; (6) Initial gasification channel; (7) Points of air injection moving along the well.

1

3 6 2

Fig. 1. A schematic of a traditional UCG gas generator. (1) Coal seam; (2) Slag and collapsed roof formations; (3) Reaction channel; (4) Air injection well cased in the coal seam; (5) Production well without casing in the coal seam; (6) Initial gasification channel.

ensures a high temperature on the surface and minimum heat emission to the surrounding rocks. The underground gas generator consists of many modules, as illustrated in Fig. 2, that are connected in single, hydraulically intertwined system. This provides a stable UCG process within the reaction channel that ensures maximum efficiency and avoids gas after burning by providing an oxidizer free exit flow.

Multiple experiments in the USA and Europe have been conducted under different geological conditions that used the CRIP technology. The CRIP technology was developed by Lawrence Livermore Laboratory [4]. Two approaches have been developed in China for UCG: chamber gasification (under the surface gasification), two-stage gasification (long tunnel, large section, two-stage). Chamber gasification consists of placing coal chambers, where the coal was first softened by means of explosions, between the injection and gas production wells. These Chinese experimenters sought to ensure sealing of every chamber of the underground gas generator. The two-stage gasification employs a two-stage implementation of the UCG process. The first stage has air injected into the underground gas generator, which is brought to a temperature as high as 1300–1500 °C, where a gasification reaction occurs. The reaction produces gas at a rate of 2500–4600 m3/h that has a combustion value of 4–6 MJ/m3. This gas was directed above ground after a second stage where steam was injected into the underground gas generator. This steam interacted with the red hot coals

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to produce blue gas having a combustion value of 9–12 MJ/m3 in a quantity of 1200–2900 m3/h. This process continues until the temperature in the gas generator falls to 700 °C; after that the process returns to the first stage activity. Linc Energy Ltd. launched its first UCG project in Australia implementing the eUCG technology developed by Canadian Ergo Exergy Inc. The Australian activity occurred in the Surat Basin near Chinchilla, Queensland. This facility used an air injection method.

3. Results and discussion 3.1. UCG in the former USSR Table 3 presents a summary of data from five operating lignite and bituminous coal UCG enterprises collected from 1947 to 1996 [1]. The process normally uses air injection. Only at the Lisichanskaya station of Podzemgaz was the injection of 28–38% oxygen implemented. The Soviet practice of gasifying coal in reaction channels, the flow method, was on the whole successful despite certain drawbacks. These drawbacks include, first of all, a low chemical and energy efficiency because the process produced low combustion value gas and suffered from relatively high underground losses of some 20%. Only 35–40% of the gasified coal energy finds its way to the consumer in this approach. The processes using seam pre-development and gasification lacked controllability. UCG at shallow depths is fraught with the risk of gases leaking above the surface through the rock mass. To prevent gas leaks a minimal pressure should be maintained within the gas generator. The traditional technology controls the process by modifying the injection and gas production volumes along with the number of engaged/disengaged wells and/or the channel length or interchannel distance. The goal is to keep the gas combustion value at 3.0 MJ/m3 or higher and the generated gas quantity within the specified range. Over a 50 year period an extensive and varied practical knowledge related to implementing underground gasification of coal seams having different properties and in different conditions was built up. This domestic UCG technology is based on the method of gasifying coal in channels. The process of gasifying coals to a depth of 250–300 m was developed to the extent that practicable application of in-channel coal gasification could be considered, even at depths from 800 to 1000 m.

As depths increase applying higher pressures for steam and oxygen injection becomes more realistic. This provides for augmented methane content and gas combustion value. The UCG method used allowed a number of techniques to be tested with some with negative results. In particular, methods requiring assisted coal breaking as well as those requiring gas and injection filtration into the pores and crevices of the coal were found to be impracticable. The viability and practicability of in-channel gasification by the flow method was convincingly demonstrated. The creation, introduction, and commercial application of traditional UCG technology involved considerable theoretical and practical effort toward studying and improving the process. Since reserves of cheap gas and oil were abundant the UCG method failed to gain a noticeable share of the national fuel consumption despite the overall positive results and rather decent economic indices (at the period of peak production in 1965– 1968). This failure was partially caused by the drawbacks of the old UCG methods. The major drawbacks of the traditional UCG technology include instability, excessive variability, and sluggish process control, as well as the low combustible value of the produced gas (3.2– 3.6 MJ/m3), the low gasification efficiency (50–60%), the considerable loss of gas and coal underground (15% and 20% accordingly), and the imperfect environmental friendliness. A desire to overcome these drawbacks stimulated development of new technology. An industrial consumer of gaseous energy is first interested in process stability; thus, the main goal was to improve this characteristic. Traditionally, during most of the operation injection occurs far from the combustion face. Contact with the fire face after injection comes about only after the introduced gas stream has been filtered through a layer of sheet, ash, and water. It is impossible to control the shape from the injection site as the flame front moves. How the forced collectors are spaced in the gasified area will determine the shape of the burn. This results in a low intensity heat-mass exchange between the oxidizer and the reaction face and the free oxidizer inevitably contacts some of the combustible gas and causes its after-combustion. The low intensity reaction in the gasification zone goes hand in hand with low temperatures and, consequently, with a low CO/CO2 ratio in the produced gas. It has been proved by practical observation in Russia that only targeted and active mass exchange between the oxidizer and the combustion face will raise the temperatures in the combustion area and, thus, the CO/CO2 ratio.

Table 3 Some major characteristics of UCG operations in the USSR. No.

Enterprise (operation years)

Lignites 1 Podmoskovnay station of Podzemgaz (1947–1962) 2 Shatskaya station of Podzemgaz (1965–1974) 3 Angrenskay station of Podzemgaz (1962–1989, operation continued) Bituminous coals 4 Yuzhno-Abinskaya station of Podzemgaz (1955–1996) 5 Lisichanskaya station of Podzemgaz (1948–1963)

Coal treated with UCG (kt)

Gas produced (106 m3)

Gas content (%) H2S

CO2

CnHm

O2

CO

H2

CH4

N2

Gas combustion value, (MJ/m3 (kcal/m3))

Gasification efficiency (%)

Gas yield (%)

Gas loss (%)

2781.8

4753.5

1.3

17.6

0.2

0.6

5.8

14.3

1.5

58.9

3.0 (720)

43.6

71.9

27.7

1000

2102,2

1.8

18.1

0.2

0.2

5.5

16.7

1.3

56.2

3.3 (790)

52.0

114.6

29.6

2350

6300

0.6

19.0

0.2

0.7

5.0

16.8

1.7

56.0

3.5 (839)

61.0

89.0

14.0

2450

10,000

0.03

14.3

0.2

0.2

10.6

14.1

2.3

58.3

4.1 (970)

55.4

91.2

13.6

750

2400

Oxygen content of the injection varied between 28% and 38%, the produced gas content varied accordingly

3.0–3.5 (700– 830)

57.0

90.0

14.8

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The required air consumption gives

5.0

LT ¼ 57=79 ¼ 0:72 m3 =m3 (1) Allowing for gas leakage from the underground gas generator the actual injection rate, L, would be

4.0

v / I (m3 /t)

η =0.5

L ¼ LT =0:85  0:85 m3 =m3

3.0

Hence gasification of 1 ton of Yuzhno-Abinskaya station coal requires the following quantity of air:

0.6

V C  L ¼ 4:2  1000  0:85 ¼ 3570 m3 =t

2.0 0.7

Production of gas with combustible value of 4.19 MJ/m3 requires an air injection, in the first case, of

0.8

1.0

3:12  3750 ¼ 11700 m3 =h and in the second

1.0

3.0

5.0 h (m)

7.0

9.0

Fig. 3. Gasification efficiency versus specific water flow and coal seam thickness.

Soviet theoreticians and hands-on experts have contributed to studies of the process and subsequent refinement of it during the development and commercialization of traditional UCG technology [1]. For example consider the Yuzhno-Abinskaya station of Podzemgaz. The UCG heat and energy efficiency depend on such factors as the coal seam thickness, the underground water flow path in the gasification area, and the intensity of air injection. In Fig. 3 each curve stands for a specific value of gasification chemical efficiency, g = QH.U.VU/QHy, plotted against the specific water flow, q = t/I. Consider the concrete example of the Podzemgaz YuzhnoAbinskaya coal seams. Assume the need to produce UCG gas with a combustion value of about 4.19 MJ/m3, QH.U., by gasifying coal seams 2 or 9 m thick. Assume the absolute water influx in the gasification zone, t, is 5 m3/h in each seam. The required intensity of the gasification process must be determined. The Yuzhno-Abinskiy coal has a QHy around 29.3 MJ/kg and so gas production may be calculated as:

C Py  22:4 Vr ¼ P  4:2 m3 =kg C r  12: where C Py is the carbon content of the coal, 75 weight percentage; nRCU the total carbon-bearing gaseous components, 33 weight percentage. In the present case the gasification efficiency is calculated as

g ¼ Q H:C: V C =Q Hy ¼ 4:19  4:2=29:3 ¼ 0:6 The relevant curve (g = 0.6) in Fig. 3 shows that a 2 m thick coal seam, at the specific water influx assumed, will produce 1.6, and a 8 m thick layer 2.6 m3/t. Hence, in the first case the required gas yield intensity will be

I ¼ 5:0=1:6 ¼ 3:12 and in the second

I ¼ 5:0=2:6 ¼ 1:92 which is in units of tons per hour. The quantity of air injected into the underground gas generator to provide this required gas yield may be calculated from the theoretical volume of air required for gas production:

LT ¼ NC =NB where NU and NB are the nitrogen content of the gas, and the air, in volume percentage.

1:92  3750 ¼ 7200 m3 =h (2) The gas generator balance is periodically updated and at that time the absolute water influx is determined for each UCG process intensity specified. One half a century of experience applying UCG technology to the gasification of lignites and bituminous coals under different geological conditions has made possible the commercial use of this gas for a number of consumers. The maximum gas output was 150–170 thousand m3/h with a gas combustion value as high as 4.2 MJ/m3. Considerable practical knowledge has been accumulated about ways to enhance stable and controllable UCG gas production at rates up to 1.0–1.5 million m3/h. Production in such volumes requires the simultaneous operation of several hundreds wells. 3.2. Experiments in the USA and Europe (1975–1995) The worldwide increase in UCG interest dates to the energy crisis of the 1970’s [5]. Experiments in natural conditions were extensively carried out in the 1980’s and 1990’s in the USA. In Europe, France, Belgium, and northern Spain, the first goal was developing methods for deep (as deep as 1000 m) coal formations. Multiple experiments in the USA proved the applicability of UCG technologies, including controlled retraction of the injection point with a moving combustion zone, the so called CRIP method. The experiments in Europe failed because of difficulties related to interlinking the wells at great depths. Among the difficulties encountered the rock pressure influence was considered the most critical. These experiments covered a limited number of operating wells, typically 2 or 3 wells. Despite the beneficial effects observed by controlled movement of the injection point along the reaction channel to follow the combustion face, CRIP technology as developed by the Lawrence Livermore Laboratory does have certain drawbacks, including: (1) Increased hydraulic resistance to the gas moving toward the vertical gas production well through the layers of broken overburden; (2) Increased thermal emission into the surrounded rock giving a consequent loss of heat when the injection point moves through the layer of broken overburden; (3) The gas yielding area surrounding the injection point cannot exceed 20–25 m. 3.3. Experiments in China, Australia, and the Republic of South Africa (1998–2010) Over the past 10–15 years UCG pilot works have been widely implemented in China, Australia, and the Republic of South Africa. Despite a scarcity of professional technical data we shall attempt to provide an overview of some of these experiments.

E.V. Kreynin / International Journal of Mining Science and Technology 22 (2012) 509–515 Table 4 Data relating to coal two-stage gasification. Mine

Commencement

Blue gas content (%) H2

CO

CH4

CO2

N2

Xinhe Liuzhuang Xinwen Xiyang

1994 1996 2000 2001

58.3 47.1 54.8 54.3

8.6 13.4 9.7 4.1

9.3 12.4 8.8 12.2

19.6 20.5 20.8 20.2

4.2 6.6 5.2 9.1

QH (MJ/ m3) 11.8 12.2 11.4 11.9

A distinctive feature of the Chinese projects was the use of gasification channels with a cut of from 3 to 4 m2 and length of up to 200 m. The mining areas were drilled with short injection and gas production wells. The support of regional governments and private coal companies allowed the implementation of six projects using this technology from 1998 to 2000. These projects included gasification of bituminous and anthracite coals at depths reaching 300 m. A low calorific value gas was produced with a combustion value of 4– 6 MJ/m3. These experiments lasted from 80 to 120 days and investments required for implementing one project amounted to 90– 450 thousand U.S. dollars. It should be noted that chamber type gasification was first applied in the USSR in 1933 to 1934 using the shrinkage method. This was replicated in the USA from 1976 to 1979 at Haw Creek. The method was proved, in both cases, to be unsatisfactory because it was impossible to reproduce in the underground coal layer the behavior observed in an above ground gas generator. The period from 1994 to 2001 saw the application of a twostage process in the form of 11 different projects. Table 4 shows data relating to some of these projects. The two-stage UCG projects implemented in China were pioneering. However, considering the impossibility of commercializing such a discontinuous process, the enthusiasm of the Chinese experts remains difficult to understand. Furthermore, the second stage, the stage of blue gas production, is very short lived and the process control system would require repeated switching from one stage to the other, especially when air injection is applied at the first stage. In 1997 Linc Energy Ltd. launched its first UCG project in Australia. Construction of the gas generator included nine vertical process wells and was completed on 12 December, 1999. The first gas was produced on 26 December, 1999, and that product had the following composition (vol.%): H2-22.85; CO-10.37; CO2-18.53; H2S0.04; N2-44.92; CH4-2.94; C2+-0.35. The pressure at the well head was kept at 1.0 MPa and the temperature was 300 °C. The maximum gas output from the generator was 15,400 m3/h, equivalent to 80,000 normalized m3/h, at a temperature of 298.14 K and a pressure of 101,325 Pa. The combustion value under stable gas production was from 4.5 to 57 MJ/m3. All this gas was flared. Testing of the underground waters at the final gas generator stage revealed the presence of benzene, phenol, and polyaromatic hydrocarbons (PAH). Samples taken directly from the gas production well exceeded the maximum admissible pollution concentrations (MAC) by 10–1000 times. Two hundred meters from the gas production well only the benzene concentration was, by a factor of 10, above the MAC. The presence pollutants 1750 m from the gas generator was below the ambient concentrations. Extremely high concentrations of benzene, 103–104 times the MAC, phenol, 107– 108 times the MAC, and PAH, 107 times the MAC, were noted in condensate from the gas stream, which suggests the possibility that the underground water will become gravely polluted in the case of considerable gas leakage from the gas generator. The gas generator was stopped in April, 2003, after 28 months of operation. During this period 35,000 tons of coal were gasified and 80 million normalized m3 of gas were produced.

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The absence of chemical pollution 200 m from the gas generator proves the practicability of maintaining pressure levels in the generator near those of the subsurface water hydrostatic column at the UCG site. Another big Linc Energy Ltd. project was another pilot production enterprise ‘‘UCG-Fischer-Tropsch synthesis’’ put into operation at the end of 2008 near Chinchilla. This plant had a liquid production output capacity of 795–1590 l/day (33–66 l/h). The gas generator consisted of nine injection and 10 gas production wells and used air injection. Gas production capacity was 10,400 m3/h. The produced gas was supplied to the FischerTropsch plant. Linc Energy Ltd. has strategic plans that include constructing a commercial UCG/Fischer Tropsch plant in southern Australia capable of producing liquid fuels at the rate of 3.2 million l/day that could be expanded to 16 million l/day. They plan to gasify bituminous coals with a moisture content of 38%, an ash content of 11%, and a sulfur content of 1%. Capital costs of this project are estimated to be $150 million U.S. The general disadvantage of the Chinchilla UCG project was the exclusive use of vertical wells, which are sure to depressurize in areas of rock shift, so that new well drilling and environment pollution are inevitable. For its first 100 day UCG project Carbon Energy Ltd. gasified high ash bituminous coal. This project occurred at the end of 2008 in Bloodwood Creek, Queensland, Australia. The coal seam thickness was 10 m and the gas generator consisted of two wells, an injection well and a gas production well. The wells were drilled in parallel across the coal seam and interconnected at the bottom in immediate proximity to the vertical ignition well. The wells were 30 m distant from one another and their bottom depth was at 600 m. The above ground complex consisted of oxygen and steam generators, a gas collector, oxygen and steam pipelines, and the gas generator control panel. This facility used steam and oxygen injection and the CRIP method for controlling the retraction of the injection point. This process had been developed and patented by the Lawrence Livermore National Laboratory and provides for control over the moving ignition point and for a stable quality of the produced gas. When decommissioned the gas generator was purified from pollutants with a specialized hydraulic circulation system. The distinct feature of this project was the implementation of an improved CRIP technology. Two boreholes in the coal seam were united into a single, hydraulically interdependent system similar to the Russian UCG technology. One channel is used for the CRIP application while the other is for discharge of the gas produced. This design solution is called ‘‘parallel CRIP’’. At the beginning of 2010 Cougar Energy Ltd. announced the successful implementation of an UCG project using air injection in the Australian state of Queensland. They gasified a coal stratum with a thickness exceeding 150 m. This project was implemented in partnership with Ergo Exergy Inc. of Canada. Future company plans call for the construction of an industrial scale UCG-CHP plant with a capacity of 400 MW. Since 2002 Eskom in the Republic of South Africa has been implementing a UCG project using the eUCG method of Ergo Exergy Inc. This project is at the Majuba coal field [6]. Here they used air injection to gasify a 3.5 m thick coal stratum at a depth of 300 m [7,8]. The project included several stages. The first stage was constructed as a demonstration module and began operation on 20 January 2007. The gas produced had the following characteristics (vol.%.): H2, 14–18; CO, 7–11; CO2, 16.5– 18.5; O2, 0.2; N2, 44–52; CH4, 2.8–4.5. The temperature at the head of the gas production well was maintained at 170 °C. The gas generator production capacity was 5000 nm3/h, and the gas produced had a combustion value of 4.1–4.8 MJ/m3.

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Initially all produced gas was flared. Since the end of May, 2007, the produced gas is being converted into electricity by a special 100 kW generator. The second stage included putting into operation a gas generator with a gas production capacity of 15,000 normalized m3/h along with equipment to pre-treat the UCG gas and to purify water. A pipeline for transporting the UCG gas to a coal fired power station was built. The gas generator started operation on 10 June, 2010. This stage involves the joint combustion of gas and solid coal in the steam boilers of the power station. The gas-fired generation presently accounts for 6 MW, which is 0.5% of the gas scheduled for use at the power station. This stage will continue until the start of 2014. The company’s strategic plans for the period up to 2014 include the construction of a gas generator consisting of 20 vertical wells capable of producing gas at the rate of 105,000 normalized m3/h. The gas can be used by the existing power station. A new demonstration UCG-CHP plant with electric capacity of 40 MW is also available to burn this gas. 3.4. New projects for the period up to 2025 Some countries have already implemented UCG projects, namely China, Australia, and the Republic of South Africa. Others have plans for implementing such projects [9]. Alaska’s Cook Inlet Region Inc. has launched a project involving the construction of a combined cycle UCG-CHP plant of 100 MW capacity in the U.S. This facility will gasify strata with total thickness of 60 m at depths of 200–1000 m. The project has been launched in partnership with the U.S. Department of Natural Resources, Ergo Exergy Inc. of Canada, and the Lawrence Livermore National Laboratory. It is scheduled for commissioning in 2014. American Energie Future has acquired a well explored site in Wyoming where UCG projects were implemented in the period from 1979 to 1995. The company plans construction of an underground coal gasification facility with a daily production capacity of 8 million liters for the synthesis of liquid fuels from UCG gas. In Canada the Alberta Provincial Government in partnership with Swan Hills Synfuels, plans to start construction of a 300 MW UCG-CHP facility in 2011. It will involve gasification of coal seems at a depth of 1400 m. This project plans for the burial of carbon dioxide within geological formations, among other things. Electric power produced by this project will be sold in the Alberta domestic markets. The investment amounts to $285 million U.S. In Great Britain Clean Coal Ltd. has obtained a license for gasification at five coal sites. The first gas generator is scheduled for commissioning by early 2014. Scottish Thornton New Energy Limited (a subsidiary of British Coal Gasification Energy Ltd.) in partnership with Australian Riverside Energy Limited has scheduled the gasification of coal at a depth of 1000–2000 m at a licensed site in Scotland. These projects also propose carbon dioxide burial within geological formations and directional well drilling. The Vietnamese National Program of supplying the domestic market with electric power and reducing coal imports is another example of UCG implementation. The projects covered by this program will be implemented by the Vietnamese Vinacomin and the Indochina Group in the Red River Delta coal fields. Presently the Vietnamese Ministry of Industry and Trade is working at the coal field preparing a development schedule for a period running until 2030. It will be submitted for Government consideration at the end of 2010. The Indian GAIL, in partnership with the Rajasthan Government and the Canadian firm Ergo Exergy Inc. has started the implementation of a UCG-CHP project involving the construction of a

750 MW combined cycle power station fired by UCG gas and located in the state of Rajasthan, India [10–15]. This project plans to gasify lignites with a high content of ash, up to 26%, and moisture, up to 40%, lying at a depth of 230–900 m. This coal is unsuitable for development by traditional methods. The seam consists of three interlayers with a total thickness of 22 m. The projects will be implemented stage by stage. At first, two stages will use two 9E GE gas turbines made by General Electric each turbine having a capacity of 175 MW electric. The third stage calls for a 9FA GE gas turbine to be installed with an electric capacity of 400 MW. 3.5. New generation UCG technology New UCG commercial technology should comply with the following requirements: (1) The injection and gas production holes of the gas generator should be located beyond the gasified coalbed overburden shift area. This will ensure their security for the entire period of operation of the gas generator. In this light, wells directionally drilled within the seam have a special advantage; (2) The gas production well coal channel should be extended to provide for a gas debit of 10–15 thousand normalized m3/h; (3) The injection supply point to the reaction channel should be moved in a controlled manner depending on the rate of coal seam gasification. The simplest way to do this is to use hydrodynamic techniques; (4) Injection and gas production wells should be united into a single hydraulically interconnected system, which will provide for the complete gasification of coals within the gas generator boundaries; (5) The maximum use of heat produced by the UCG underground generator requires UCG gas recuperative cooling within the gas production hole. This is an efficient solution for this heat exchange task; (6) Coal gasification should be highly intensive so that a gasification rate of 2.5–3.0 tons of coal per hour per well will be obtained. This will provide a high temperature in the gasification zone and, thus, maximum recovery of combustible matter, i.e.; CO and H2; (7) The interconnection of the operating well bottoms at depths exceeding 400–500 m under the influence of rock pressure is possible only with the application of special technical solutions; (8) The minimization of adverse influences on the rock formation and subsurface waters is achievable via regulation of the gas generator pressure dependent on the subsurface water hydrostatic column within the gasification area; (9) Water pumped from the gas generator should be purified chemically in an above ground complex, and biologically directly within the gas generator.

4. Conclusions (1) An interest in the implementation of UCG techniques for the production of electricity and synthetic hydrocarbons is growing worldwide. (2) A considerable number of UCG projects implemented within the last 10–15 years has proved the strategic importance of developing this technology. Hundreds of millions of dollars have been invested by many countries to ensure their own energy independence on imported natural gas and oil in a safe way. (3) These are pilot projects, however. Pilot works often fail to attain industrial standards or a level of advanced development required for the new generation UCG technology. On the other hand it is possible at the very start to use the highest efficiency solutions recently designed and patented in Russia (1996– 2010). It is practicable to commence contemporary UCG projects in Russia and in foreign countries such as the USA, Canada, Great Britain, India, or Vietnam using this best available technique that will allow bringing projects closer to an industrial scale.

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(4) Gazprom promgaz new generation UCG technology has been described in the recently published monograph Underground Coal Gasification: Theoretical and Practical Foundations, Innovations and in the Russian patent literature.

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